04. Modules and Code Structure

File structure:

The structure of the repository solver is given by

├── README.md
├── .gitignore
├── fpm.toml
├── settings.input
├── app
│   └── main.f90
├── src
│   └── equations
│   │   └── 2D.f90
│   │   └── builder.f90
│   │   └── definitions.f90
│   │   └── definitions_test.f90
│   └── maths_constants
│   │   └── diff_coeff.f90
│   │   └── fundamental.f90
│   └── Newtons_method.f90
│   └── domain.f90
│   └── equations.f90
│   └── maths_constants.f90
│   └── linear_algebra.f90
│   └── reader.f90
│   └── solve_bvp.f90
│   └── solve_ibvp.f90
│   └── type_kinds.f90
├── test
│   └── check.f90
│   └── test_collection_BVP.f90
│   └── test_collection_lapack.f90
├── examples
├── build
└── LICENSE

• .gitignore tells git to ignore certain files
• fpm.toml sets the FPM and complier settings
• settings.input contains the solver settings and parameters
• The directory app contains the main parts of the program
• All remaining Fortran files are in the src directory
• It's important to note that the names of the modules inside src/equations are given by equations_2D, equations_builder, etc
• The directory test contains all the testing subroutines
• The directory examples contains all example equation files. Used in Section 9
• The directory test contains all the module executables. This can be cleaned with the command fpm clean.

General Overview:

Here is a general overview of the solver. Each node is it's own subroutine. The order of operations goes from left to right, up to down. If there is a double arrow then the new subroutine returns back to the original subroutine without calling any other significant subroutines.

We have not described every subroutine here - for example the subroutines domain.f90: initial_domain_settings and equations.f90: equation_setup will be described in Section 7.

Note that main.f90 is in the directory app. All other .f90 files are in the folder src.